1. Technical Field
The present invention relates to a piezoelectric element having a horizontal electrode structure or the like.
2. Related Art
Piezoelectric elements, such as ultrasonic transducers for performing conversion between an ultrasonic wave and an electrical signal are known in the art, including piezoelectric elements having a vertical electrode structure in which electrodes are provided on the upper and lower surfaces of the piezoelectric body. One example of such piezoelectric elements is found in Japanese Patent Document No. JP-A-2002-271897. The principle of a piezoelectric element that receives an ultrasonic wave to generate an electrical signal is that the piezoelectric body having received an elastic wave of an ultrasonic wave is distorted, surface charges are generated due to the distortion, and a potential difference (voltage) occurs between two electrodes.
As the structure of the piezoelectric body, not only the vertical electrode structure but also a horizontal electrode structure is known, in which two electrodes are provided on the one side surface of the piezoelectric body. A piezoelectric element having a horizontal electrode structure has an advantage that reception sensitivity is good compared with the piezoelectric element having a vertical electrode structure.
For example, a piezoelectric element is used in an ultrasonic measurement apparatus that measures biological information by irradiating the human body with ultrasonic waves and receiving the reflected waves. In the ultrasonic measurement apparatus, as the irradiation intensity of the ultrasonic wave becomes higher, the reception intensity becomes higher. Accordingly, more accurate biological information is obtained. However, in order to minimize the influence on the human body, the irradiation intensity needs to be as low as possible. For this reason, there is a need for further improvements in the reception sensitivity in a piezoelectric element that receives reflected waves of ultrasonic waves.